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void GraphicsView::mousePressEvent(QMouseEvent * event)
{
    if(event->button() == Qt::LeftButton)
    {
        pressPoint = event->pos();
        isPressed=true;
    }
    QGraphicsView::mousePressEvent(event);
}

void GraphicsView::mouseMoveEvent(QMouseEvent *event)
{
    if(isPressed)
    {
        int oldX = pressPoint.x();
        int oldY = pressPoint.y();
        int newX = event->pos().x();
        int newY = event->pos().y();

        newX=(oldX-newX);
        newY=(oldY-newY);

        int verticalScrollValue = this->verticalScrollBar()->value();
        verticalScrollBar()->setValue(verticalScrollValue +newY);
        int horizontalScrollValue = this->verticalScrollBar()->value();
        horizontalScrollBar()->setValue(horizontalScrollValue +newX);

        qDebug()<<newX<<newY;
        qDebug()<<verticalScrollValue<<horizontalScrollValue;
    }

    QGraphicsView::mousePressEvent(event);
}

void GraphicsView::mouseReleaseEvent(QMouseEvent *event)
{
    isPressed=false;
    QGraphicsView::mouseReleaseEvent(event);
}